Stucture And Properties Of In, Tm Codoped LiNbO₃ Crystals With Varied Indium Concentration

In:Tm:LiNbO₃ crystals with varied indium concentration were grown by the Czochralski method. The structure, spectral properties, occupying mechanism and optical damage resistance of In:Tm:LiNbO₃ crystals with varied indium concentration have been systematically investigated by XRD, IR absorption spectra, ultraviolet-visible absorption spectra, emission spectra and transmission photospheric facula deformation method.The results show that in In:Tm:LiNbO₃ crystals, In³⁺ ions replace the antisite Nb and vacancy Li firstly. When the In³⁺ concentration reaches the threshold value concentration, almost all the Nb_Li⁴⁺ ions are replaced by In³⁺. When the doping concentration of In³⁺ is over the threshold concentration, the In³⁺ ions begin to replace the Nb sites.As the concentration of In³⁺ increases, the defect density in the crystal increases. Meanwhile the optical damage resistance of the crystal get stronger. NbLi, the electron traps, vanish as the In³⁺ concentration reaches the threshold value concentration, and the optical damage resistance becomes the strongest.Based on the vacancy Li modal, we calculated the threshold value concentration as 1.53mol% according to the principle of charge balance. However the actual value is 3mol%. We supposed that this discrepancy demonstrates the existence of interstice In.359nm(³H₆â†'¹D₂), 475nm(³H₆â†'¹G₄), 695nm(³H₆â†'³F₃), 793nm(³H₆â†'³F₄) absorption peaks were observed. Transition processes of the energy levels of Tm³⁺ were analyzed in details.Excited by 360 nm light, 463nm(¹D₂â†'³H₄) emission peak was observed. Excited by 720 nm light, 469nm(¹D₂â†'³H₄) and 613nm(¹G₄â†'³H₄) up-converse emission peaks were observed. Mechanism of up-conversion above were ESA(excited state absorption).